In many environments, the structural integrity of certain critical components of a particular system or apparatus is of the utmost importance in ensuring against future failures. For example, components used in the construction of large turbines are typically subjected to great mechanical stresses and must be able to withstand exposure to extreme temperatures as well as high velocity corrosive gas streams. Accordingly, to provide high performance characteristics and improve the reliability of a turbine, strict requirements are imposed on the structural integrity of its constituent parts. In this regard, the use of various ultrasonic examination techniques has proven to be advantageous in providing useful information concerning the internal structural integrity of part forgings. In particular, two ultrasonic inspection techniques used for the nondestructive testing of turbine rotor forgings include a "Pitch-Catch" technique that employs a pair of ultrasonic transducers and a "Pulse-Echo" technique that uses only a single transducer. Conventional manual testing techniques relied upon an operator to observe a CRT and manually record all occurrences of an ultrasonic echo exceeding a predetermined threshold. The present invention concerns improvements to ultrasonic testing arrangements of the above sort that utilize automated computer controlled data acquisition techniques. A primary motivation to automate ultrasonic rotor testing was to improve the detection of "indication structures" (i.e., potential structural flaws or voids) and reduce operator induced variability of test data results. Although an automated system substantially removes operator variability, it requires a certain degree of signal processing and analysis to distinguish between real signals and noise. Computer-controlled automated testing arrangements are ideally suited to provide the needed signal processing and analysis. Accordingly, the present invention as described below provides improved automated data acquisition techniques and control electronics for use in computer-controlled ultrasonic testing systems.
In FIG. 1, the basic mechanical arrangement, 100, of an ultrasonic diagnostic system used for examining a turbine rotor is illustrated. In addition, a block diagram of the data acquisition and control system electronics, 130, in accordance the present invention is also shown. Although the system depicted in FIG. 1 illustrates a "pulse-echo" testing arrangement that requires only a single transducer, the improved data acquisition and control system as contemplated by the present invention is also applicable to testing arrangements utilizing multiple transducers, for example, a "pitch-catch" or other diagnostic technique.
During ultrasonic testing, a turbine rotor forging 110 is rotated by electric motor driven mechanical rollers ("power rollers") 120 and 121. An ultrasonic transducer 125, located at the end of a support arm, is capable of controlled movement relative to the rotor axial direction. The speed of the rotor rotation, starting position and motion of the transducer, as well as the ultrasonic return soundings data received by the transducer are respectively controlled and processed by data acquisition and control system 130. In the improved data acquisition and control system arrangement contemplated in accordance with the present invention, the motion control circuitry 149 and motion control signal amplifier circuitry 150 for the transducer positional servo (or stepper motors) and the power driving roller 120-121 are preferably located on one or more modular plug-in circuit boards ("circuit cards") associated with a system diagnostic and control computer, 131. While the rotor is being rotated, pulser-receiver unit 140 stimulates one or more transducer 125 to generate ultrasonic pulses and also monitors the same to receive ultrasonic soundings for storage and analysis. Diagnostic data is acquired in the form of ultrasonic soundings produced and received through transducer 125 via ultrasonic pulser-receiver unit 140. Signals from transducer 125 are converted from analog to digital form by A/D (analog-to-digital) signal converter 141 and stored in a memory 142 associated with the A/D circuitry. The stored digital signals are then transmitted on request to diagnostic and control computer 131 for processing. System computer 131 also may then compress these digital signals and store them as data records in a more permanent storage medium 132.
In accordance with the present invention, the flexibility of the diagnostic system is enhanced by the provision of a modular computer-controllable pulser-receiver that is capable of providing ultrasonic pulse generating functions and signal amplifying functions either separately--as would be available, for example, through independent circuit modules--or in concert as a single instrument under computer control. Accordingly, pulser-receiver unit 140 of the present invention preferably consists of one or more modules or circuit cards that plug (connect) into a "mother" board (i.e., a circuit board that has suitable electrical buses for providing power, ground, signal data and the like between several cards or modules) for easy access, removal and/or replacement. The pulser-receiver unit mother board (not shown) and its associated plug-in circuit cards are preferably contained within a suitable electrically shielded housing (not shown) to minimize the radiating of electrical noise. In the example arrangement of the present invention shown in the accompanying figures, an ultrasonic pulse generator and pulse duration controller circuit ("pulser control") and a transducer position control logic circuit ("relay control logic") are combined together as an integral module on a single circuit card, although other divisions of function and/or modular arrangements are also possible. In accordance with one aspect of the present invention, the "pulser control" generates ultrasonic pulses of specific durations and also allows either manual or computerized control over the direction (angle) of the ultrasonic beam. A separate circuit card module contains an analog logrithmic amplifier circuit that provides selectable logrithmic amounts of signal gain for both video and RF compatible outputs. Preferably, the mother board is outfitted with a plurality of signal/power bus interface connectors for easy addition of other custom function modules as desired--such as another ultrasonic signal amplifier card, a CRT display driver card, or the like.
In accordance with another aspect of the present invention, A/D converter 141 and associated memory 142 of the present invention are preferably provided on "plug-in" type circuit boards associated with system computer 131. In accordance with still a further aspect of the present invention, a data acquisition and control system arrangement is presented that can easily accommodate multiple pulser-receiver modules to provide individual or cooperative use of several ultrasonic transducers such as used, for example, in a "pitch-catch" diagnostic technique.
Previous to the present invention, pulser-receiver functions were obtained by using a General Electric (GE) AMPUT.TM. Pulser/Receiver unit or a printed circuit board version of this unit. Although the GE AMPUT.TM. Pulser/Receiver performs satisfactorily in manually controlled ultrasonic testing arrangements, its fixed hardware design does not quite provide a degree of flexibility which would permit a more comprehensive utilization of the many capabilities that a computer controlled data acquisition arrangement can offer. For example, although the GE AMPUT.TM. Pulser/Receiver is triggerable from an external source (e.g., a remote computer), its constituent circuit functions and settings are not directly computer controllable. It is not possible to select and vary operating parameters such as gain, sensitivity, frequency range, etc., either remotely or under programmed control. Moreover, it is not possible to easily modify the ultrasonic signal amplifier response characteristics or utilize the signal amplifier and pulser functions individually or independently of one another may be required, for example, in non-ultrasonic applications.
Often, during an ultrasonic examination of turbine parts, it is desirable to be able to rearrange the relative positions of ultrasonic transducers including the transducer housing/coupling support mechanisms and/or the overall physical configuration of the test equipment to accommodate new or different components, testing procedures and/or applications. When using the conventional GE AMPUT.TM. Pulser/Receiver unit, such flexibility is not readily achievable. Therefore, in accordance with the present invention, an improved pluser-receiver is provided that can be operated as separate modules performing respective "pulser" and "receiver" functions or as a single integrated pulser-receiver unit. Moreover, the pluser-receiver electronics of the present invention may be operated independently of the rest of the ultrasonic test equipment as a stand alone instrument. The modular "plug-in" architecture of the improved pulser-receiver of the present invention also allows test configurations that need to use multiple pulser-receiver circuit pairs for operations with multiple transducers.
Accordingly, the described embodiment of the present invention provides an improved pulser-receiver that results in a configuration variable ultrasonic testing system and provides an improved operator interface method for the computerized operation and control of ultrasonic testing equipment. In addition, the present invention provides a menu-driven interactive operator-machine interface means for the system control computer that is compatible with the improved pulser-receiver for configuring the ultrasonic test equipment and controlling pulser-receiver functions.